Well, I don't know about the skin against the sleeping bag, since I have good thermals and I like being able to roll out of the sleeping bag without getting a chill. The only way I'll do that is if I'm sharing a sleeping bag with the right person.
You can also have a bottle to piss in (this needs to be a bottle that closes very securely and is different enough from your drinking water bottles) since it also functions as a hot water bottle.
Crumpled newspapers can function as extra insulation, as can paper towels, dry grasses, leaves, etc.
Always take off your shoes/boots, because you want all the blood flow available to your toes so you don't get frostbite- tight clothing is a big no in cold weather in general.
Brush and tall plants will serve as a wind break and will cut down on wind chill.
Being under a bridge is better than being under an open sky, because the it will reflect more of your heat back down on you.
With pallets, cardboard, newspapers and/or plastic bags you can make a pretty warm but cramped shelter.
And lastly, ask your questions way ahead of time instead of procrastinating so much.